1. Field of the Invention
The present invention relates to hard shell tubular bats having an exterior shell of metal or composite, and more particularly, to aluminum baseball bats which currently are used at the college and lower levels. Such bats typically include a metal shell formed of resin composite, aluminum or titanium alloy or other metals, such bats being used not only in baseball but also in softball at such substantially all levels of non-professional levels of play. As referred to herein, the terms xe2x80x9caluminumxe2x80x9d and xe2x80x9ctitaniumxe2x80x9d are intended to encompass the metals and alloys and mixtures of metals and alloys formulated for the manufacture of bat shells.
Recently, the National Collegiate Athletic Association (NCAA) has indicated that, for player safety reasons, the batted ball exit speed for non-wood bats should equate to or not exceed the highest average exit speed using major league baseball quality, 34 inch solid wood bats. Bats meeting these specifications are expected to result in lower incidences of harm to ball players and moderate the game offense. A typical 34xe2x80x3 wood bat has a moment of inertia in the range of about 10,500-12,000 oz.-in.2 and it is therefore contemplated that tubular hard shell bats should have a moment of inertia not less than 10,500 oz.-in.2 or thereabout. Moment of inertia testing is performed by determining the bat weight in ounces and the balance point location in inches then pivotally supporting the bat 6 inches from the knob end to swing as a pendulum and and timing the average swing period over not less than 10 cycles.
2. Prior Art
Tubular bats formed of a hard outer shell and a reinforcing or shock dampening inner layer which may comprise solidified foam therein are known. For example, U.S. Pat. No. 5,395,108 Souders, et al issued Mar. 7, 1995 for a SIMULATED WOOD COMPOSITE BALL BAT comprises a fiber reinforced composite shell filled with expansible urethane foam to develop compressive stresses therebetween and U.S. Pat. No. 5,364,095 issued Nov. 15, 1994 to Easton, et al discloses a tubular metal ball bat internally reinforced with fiber composite.
U.S. Pat. No. 5,114,144 issued May 19, 1992 to Baum discloses a composite baseball bat made to look like a wood bat by using a central core of foamed plastic (foam density of 5-15 lbs/cu. ft.) or extruded aluminum covered with a layer of resin impregnated fiber knitted or woven cloth and a surface layer of longitudinally extending planks or strips of resin coated wood veneer; U.S. Pat. No. 5,458,330 issued Oct. 17, 1995 to Baum discloses a composite bat having a wood veneer surface and cavitied foam core; and U.S. Pat. No. 5,460,369 issued Oct. 24, 1995 to Baum discloses a composite bat having a wood veneer surface bonded to a composite tubular core. Also, U.S. Pat. No 5,533,723 issued Jul. 9, 1996 to Baum discloses a composite bat having a wood veneer surface and intermediate composite layer bonded to a tubular core of composite or aluminum. The core may comprise a resilient urethane foam and a cavity may be left in the core in the hitting area and the cavity may be filled with less dense material. The core may vary in density over the length of the bat, preferably with a higher density section near the barrel end.
The primary objective of the invention is to provide a durable hard shell baseball bat in which the ball rebound characteristics approximate those of a wood bat by emulating the longitudinal flexibility and cross sectional rigidity characteristics of a wood bat of similar size and shape whereby the speed of the batted ball is approximately the same as would be experienced with a wood bat of similar weight, shape and size.
The present invention provides a governed performance ball bat comprising:
a) a tubular exterior shell having a maximum outside diameter in a ball hitting area and a ratio of said maximum outside diameter to the wall thickness of the shell in the hitting area in the range of from 40:1-90:1; and
b) a filler contacting and internally supporting an annular interior surface of the bat shell in the hitting area, said filler having a sectional density in the range of 10-30 lbs./cu. ft. and a hardness on a Shore D test apparatus in the range of 25-65.
The present invention further provides a governed performance aluminum shell ball bat comprising:
a) an aluminum alloy shell having a ratio of maximum outside diameter to the wall thickness of the shell in the ball hitting area in the range of from 45:1-75:1; and
b) a foam material contacting and internally supporting the bat shell in the hitting area, said foam having a sectional density in the range of 10-30 lbs./cu. ft. and a hardness on a Shore D test apparatus in the range of 40-65, said bat having longitudinal flexibility characteristics approximating those of a wood bat of identical geometry.